A conventional starter for use in starting a vehicular engine has been constructed as shown in FIG. 1.
The conventional engine starter 1 shown in FIG. 1 comprises a d.c. motor 2, an over-running clutch assembly 4 slidably mounted on an armature rotary shaft 3, a gear unit 5 for reducing and transmitting the rotating force of the armature rotary shaft 2a of the d.c. motor 2 to a clutch outer member 4a of the over-running clutch mechanism 4, and a shift lever 8 engaged at its one end with a plunger rod of a solenoid switch assembly 6 which is disposed on one side of the d.c. motor 2 for axially moving the over-running clutch assembly 4 and at its the other end with an annular member 7 mounted to the over-running clutch assembly 4.
However, during the starting of an internal combustion engine, high torque is required at the initial stage and low torque and high speed are required after the initial combustion. With a conventional starter having only a fixed speed changing ratio, more torque is needed at the initial stage of starting and more rotating speed is required after initial combustion. Therefore, a starter employing a belt-type stepless speed changer such as the one disclosed in Japanese Utility Model Laid-Open No. 58-172058 has been proposed.
However, in the starter with the belt-type stepless speed changer as disclosed in the aforementioned Japanese Laid-Open document, a problem of power loss due to slipping is posed and, since the load change is great between the compression stroke and the combustion stroke of the piston particularly in starting the engine, the belt slips easily, resulting in very poor transmission efficiency as compared to an ordinary starter.